Welcome to the United Sorghum Checkoff Program's Mid-South Production Handbook. We have integrated research from various sources to produce an easy-to-use guide that can help farmers manage their crop more efficiently. Sorghum has tremendous potential to return a profit to your farm and the work of the Sorghum Checkoff will only improve that potential over time. As you manage your sorghum, keep these tips in mind:
By following a few guidelines, you'll be amazed at what this crop can do for you. We strive to help you make sorghum more profitable for your operation. But remember, every situation is a bit different so contact your local county extension office, land-grant university or other area sorghum farmers to help you get the most out of this water-sipping crop.
Produced and edited by:
United Sorghum Checkoff Program
Growing Grain Sorghum in North Carolina, 2009
North Carolina Cooperative Extension Service
North Carolina State University
College of Agriculture and Life Sciences
North Carolina Small Grain Growers Association
United Sorghum Checkoff Program
4201 N. Interstate 27,
Lubbock, TX 79403
It is important to understand the various developmental stages of sorghum since this understanding will assist in making irrigation and management decisions. The stages are based on key stages of sorghum growth that are used to describe sorghum from planting to maturity (Figure 1).
Another common scale that is used among sorghum researchers is a more simplified growth scale. GS1 would equate to stages 0-5 (vegetative stage) in this system. GS2 would represent from stages 5-10 (reproductive stage), and finally, GS3 would be from stage 10 to 11.5 (flowering stage).
Comprehensive grain sorghum growth and development guides are available, such as Kansas State How a Sorghum Plant Develops (currently being revised with your Sorghum Checkoff dollars) and Texas AgriLife How a Sorghum Plant Grows. Both of these guides provide pictures of different growth stages, graphs of cumulative nutrient uptake relative to growth stages (KSU), or approximate heat unit requirements (base temperature 50°F, maximum 100°F) for attaining a particular growth stage (Texas AgriLife). Cool or wet weather early in the season or an early planting date can significantly slow growth early in the season adding a week or even two weeks to the time to half bloom.
The planting period for grain sorghum is very wide. Research in Virginia and North Carolina has shown that high yields can be obtained from planting dates ranging from May 1 to July 1 (Fig. 2). Optimum planting dates for consistent yields fall from May 10 to June 15. Double-cropped sorghum could be planted as late as July 10, but later dates result in a crop that will not mature until late fall and will increase the risk of an early fall frost damaging the crop. Generally, on sandy soils that are more drought prone, an early planting date (early to mid May) is the best choice. This gives the crop plenty of opportunity to reach head exertion without the risk of moisture stress. However, sorghum has been grown successfully as a double-crop behind potatoes, barley or wheat on both mineral and organic soils. The keys to acceptable yields when planting sorghum as a double-crop behind potatoes or wheat are to select an early to medium-maturing hybrid and to plant in narrow rows.
Hybrid selection is critical to the success of the sorghum crop. Hybrids can be broken into three categories: early, medium, and late. Generally, early hybrids reach flowering in 45 to 55 days. Medium hybrids flower in 55 to 65 days and late hybrids take longer than 65 days to flower. Most of the hybrids available in North Carolina are late hybrids. Research trials have shown that on soils with good water holding capacity or when sorghum is grown in years with good rainfall, late hybrids work well. Good examples are AgriPro AP2838, DeKalb DKS44-41, and Pioneer 83G66. However, when planting sorghum on droughty soils or when planting as a double-crop behind Irish potatoes, wheat, or barley, early to medium hybrids work best. Early hybrids reach flowering before water stress sets in and can reach maturity before a frost.
Currently there is no official variety test for grain sorghum. Producers should rely on local tests or use on-farm comparisons to identify the best hybrids for their soils. Table 1 shows the results of a hybrid performance trail conducted in 2008. While limited to only a few hybrids this is the latest information we have for hybrid response on sandy soils.
Table 1. 2008 sorghum hybrid comparison trial. Anthracnose ratings for sorghum hybrids grown in North Carolina. 1 = poor diseases resistance; 10 = excellent resistance. Maturity refers to the number of days to flowering or mid-bloom.
The following list describes recommended sorghum hybrids based on recent information and analysis. Use this list to help identify potential sorghum hybrids.
WARNING: This list of hybrids is based on information from field trials, county variety tests, and other field observations. As such it represents the best information available. However, this is not a comprehensive list. There are several companies that have sorghum hybrids that have not been tested in North Carolina. The hybrids offered by these companies may have characteristics that are as good or better than the listing below. The grower should evaluate these hybrids by comparing the literature offered by the company to the information given below.
Seeding should be done in seeds per acre NOT POUNDS PER ACRE. Like wheat, sorghum seed varies greatly in the number of seeds per pound and this can impact the number of plants seeded. In most cases, sorghum should be planted to achieve final plant populations of 100,000 to 120,000 plants per acre (Figure 3). At 75% emergence this would require 130,000 to 160,000 seeds planted per acre (Table 2). However, when planting on droughty or sandy soils seeding rates should be reduced to achieve final a plant population of 90,000 plants per acre. Emerging sorghum seedlings are fragile and can be easily destroyed by insect feeding or soil drying. Percent emergence will often be less than 75% when planting in cool, wet soils or when planting using no-till practices. When planting early or when planting under no-till conditions use of an in-furrow insecticide or Gaucho® or Cruiser® seed treatment is recommended.
When planting between May 1 and June 1, row widths from 10 to 20 inches yield the best (Figure 4). Row spacings of 30- or 36-inch rows have less yield potential. However, on extremely droughty soils, 30-inch rows can give more consistent yield results from year to year. This is due to the fact that water can be stored in the middle of the interrow area and is available during heading and flowering when the sorghum plant's need for water is the greatest. When planting after June 1, sorghum yield tends to be greater when drilled at spacings less than 15 inches.
|Sandy||Organic or Piedmont Soils||Irrigation|
|Target Plant Populations (plants per acre)|
|When Planting after June 15th increase seeding rates by 20,000 seeds per acre assumes 70% emergence|
|When planting in good to ideal conditions emergence will be 85% or greater. Reduce seeding rates accordingly.|
Grain sorghum requires less nitrogen than corn, but has similar requirements for P and K. Between 30 to 50 lbs of P2O5 per acre and 50 to 70 lbs or K2O are recommended for sorghum based on soil test levels. Sorghum does not respond well to starter fertilizer with P and K. It is better to have sufficient levels of P and K in the soil prior to planting than to supplement.
Nitrogen rates for optimum sorghum yields range from 80 to 125 lbs of N per acre (Figure 5). In heavy residue or when little or no nitrogen is available from the previous crop, some nitrogen applied in a band at planting can be beneficial. Otherwise, the best time to apply nitrogen to grain sorghum is at sidedress (sorghum is 10 to 12 inches tall). On most soils 120 lbs of N per acre applied at sidedress will produce excellent results. Nitrogen fertility is important for high sorghum yields. Nitrogen must be available from 12 inches to flowering for a good sorghum crop. Lack of nitrogen at heading can result in failure to set seed (head blasting).
The best option for weed control on organic or mineral organic soils is to use Concept treated seed (safened seed) and a mixture of Dual and atrazine at 1 to 1.33 pt of Dual and 1 to 1.5 qt atrazine. Another alternative is to use safened seed and Lasso (Intro) and atrazine. On organic or mineralorganic soils a post-emergence application of atrazine + Clarity is very effective in controlling most broadleaf weeds but is limited in grass control. On sandy soils with less than 1% organic matter the only alternative is to use safened seed with Lasso (Intro) or concept treated seed with Dual and then follow with a post emergence application of 2,4-D + Clarity. Post emergence applications of 2,4-D and Clarity can be very effective. Sorghum should be treated after it is 4 to 6 inches tall but before it reaches 12 inches. The chemical manual states that sorghum is more sensitive to 2,4-D or Clarity than corn. This is true if 2,4-D or Clarity is applied after sorghum is 12 inches tall. Before this stage, sorghum is actually more tolerant to these chemicals than corn.
For grass control Buctril can also be applied post emergence up to 14" tall. Unfortunately, Buctril is not effective against common grass species such as nutsedge, bermudagrass, and goosegrass. In severe cases, Lorox or Evik could be applied using drop nozzles to clean up a grass problem. Some damage to the sorghum crop will occur when using these products.
The two main pest problems in grain sorghum are birds and corn earworm. Bird damage can be avoided by planting large areas and avoiding planting small fields near heavily wooded areas. There are no easy methods of getting rid of birds. Bird-resistant sorghum hybrids are available but have less desirable feeding characteristics and are usually discounted at the market. Corn earworms can be a significant problem. Earworms attack the flowers and kernels of sorghum. In early August, earworm moths move from maturing corn fields and attack sorghum that flowers from August through early September. The damaging pest is the hairy caterpillar that is usually light green, tan, or yellow with a broad lighter strip down the side. It has small black spots, an orange head, and curls up when disturbed. Sorghum, particularly sorghum planted after June 1, should be scouted for corn earworms from flowering to maturity. Earworms can be easily controlled through the use of insecticides such as Warrior®. However, significant damage often occurs before the problem is recognized and treated.
There are few other significant insect pests that effect grain sorghum in North Carolina. Billbugs do not reproduce on grain sorghum. However, they have been known to feed on small sorghum plants. It is rare to find significant billbug damage to sorghum. There are several diseases that can affect sorghum such as Fusarium head blight. Probably the most damaging disease is anthracnose. This is a common disease in cereal crops in North Carolina. The most common way to manage this disease is through variety resistance. Unfortunately, there are only a few sorghum hybrids with good resistance to this disease. Growers who are growing sorghum after corn or a previous sorghum crop should choose sorghum hybrids with good resistance to anthracnose.
Anthracnose Leaf Blight and Stalk Rot of Sorghum
Anthracnose is caused by the fungus Colletotrichum graminicola (Ces.) G.W. Wils., teleomorph Glomerella graminicola Politis. When this disease occurs on sorghum it is commonly divided into three categories based on where symptoms develop on the plant. The three categories are: leaf anthracnose, panicle and grain anthracnose and anthracnose stalk rot. Cultivated hosts include sorghum, sudan grass, wheat, oats, rye and barley. The fungus also has several grass hosts. Those hosts of importance in North Carolina are crabgrass, Johnson grass, orchard grass and red fescue. While C. graminicola has a wide host range, isolates from small grains do not infect corn and sorghum. However, corn isolates have been shown to infect sorghum and Johnson grass. The fungus survives readily as mycelium and spores on plant debris that remains on the soil surface. Fungal viability is diminished when debris is buried. The fungus also survives between seasons in seed. It is suspected that it overwinters as hyphae and/or stroma in the endosperm. Primary infection of leaves occurs when conidia are windblown or splashed from debris to leaves. Conidia germinate and infection occurs directly through the epidermis or through stomata. The infection process takes place readily when warm wet weather conditions prevail. Primary infection is not as clearly understood in the stalk rot phase of the disease. The confusion is partially due to the fact that stalk rot can occur in fields with very little leaf blight and little or not crop residue from the previous year. The infection may spread from leaf sheaths to stalk tissue or the disease may progress from the roots up the plant. In the latter case, the source of inoculum is suspected to be resting spores that have overwintered in buried stalk debris. In addition, the fungus may enter stalk tissue through insect feeding wounds.
Colletotrichum graminicola produces a wide range of symptoms on sorghum. Leaf blight symptoms progress from lower to upper leaves and vary in size and color with host genotype. Typical symptoms on a susceptible hybrid appear as small, water soaked spots that are semitransparent and oval to elongate in shape. Spots enlarge and become tan with a wide border that is varies in shade from red or orange to purple or tan. The entire leaf may become blighted if lesions coalesce, resulting in a "fired" appearance. Dark fruiting bodies called acervuli develop on dead host tissue. When large numbers of acervuli form, they may be present in concentric rings. Black hairlike structures (setae) and conidiospores form in the acervulus. Conidiospores appear creamy to pink-ish color when they are present in large numbers and serve as the source of inoculum for secondary infection. Leaf infection may also appear as a midrib infection. This type of infection is characterized by elongated elliptical lesions that vary in color from red to purple to black. Acervuli may also be present in these lesions. Leaf and midrib infections may occur independently of each other or together in which case yield loss increases. Leaf anthracnose generally occurs at half-bloom or later. If plants are infected early in the growing season, damping off may occur or plants may be stunted, yellow and tiller poorly.
Panicle and grain anthracnose occurs on mature plants. Spores of C. graminicola produced from the leaf blight stage are splashed by rain or irrigation water to the panicle (inflorescence) and initiate infection. Initial lesions are water-soaked and turn tan or purple with age. They are elliptical or bar shaped and occur just below the epidermis. If the panicle is split lengthwise, areas of red discolored infected tissue can be seen interspersed with healthy white tissue. Black acervuli may be produced in infected tissue and extend on to seed produced on the panicle. Infected panicles are lightweight, may exhibit some degree of sterility and mature early. Infected seed is discolored, germinates poorly and may produce plants that succumb to seedling blight.
The stalk rot phase of anthracnose is very similar to the panicle infection phase. Infection may occur at anytime during the growing season but symptom development is most common on mature plants. Infection occurs when conidia from the leaf blight stage are splashed or wind blown to the stalks. The initial symptom of stalk infection is a water-soaked discoloration of rind tissue in the lower internodes. Lesions take on a reddish discoloration and infected tissue is interspersed with healthy tissue. External infections are characterized by irregular bleached areas that are surrounded by a red border (host pigmentation).
Resistance is available for both the leaf blight and stalk rot phases. However, hybrids showing resistance to anthracnose stalk rot often do not show resistance to stalk rots caused by other fungi.
Anthracnose is generally more severe on continuously cropped corn where residue remains on the surface between seasons. Burial of residue has been shown to be effective in reducing inoculum. Residue burial would be most effective when rotating to a nonhost crop such as soybeans. In a conservation tillage system with continuously cropped corn, destruction and burial of residue is not possible so selection of a resistant hybrid would be necessary.
Seed protectant fungicide, thiram is labeled for control of seedling blight on sorghum. Trials have indicated that seed treatments are effective at preventing early infections and can help reduce the incidence of the stalk rot phase of anthracnose.
Ideally, sorghum should be harvested at 16-18% moisture and dried down to 13.5%. This gives an excellent quality grain with less potential for lodging. However, if drying facilities are not available, sorghum can be left to dry in the field. Sorghum should be stored below 13.5% moisture. Careful attention should be given to checking stored grain sorghum regularly. The small kernels leave less air pores in the bin and can lead to trapped moisture and "hot spots" where stored grain insects will multiply rapidly.
An efficient harvest is the result of attention to management throughout production and harvest seasons. Decisions, such as the selection of hybrids that mature at a time when labor and equipment can be devoted to harvest can ensure that the sorghum produced in the field makes it to the bin. Since sorghum is a perennial it has the potential to produce tillers in the fall that are generally undesirable. Therefore, sorghum producers should select hybrids that will mature just prior to the first killing frost with the goal of harvesting the crop as soon as it dries to 18% moisture. Estimates have put average sorghum harvest losses in North Carolina anywhere from 5 to 10 bushels per acre, with expert operators and managers reducing this to about 1 to 2 bushels per acre. The added income from an efficient harvest is almost pure profit, so a timely harvest and the few minutes spent on careful combine adjustment can be extremely profitable. The key to maximizing sorghum quantity and quality is timely harvest.
1) Timely harvest reduces the potential losses to bird feeding, 2) reduces the chance of lodging from a hurricane or tropical storm, and 3) improves grain quality by reducing losses resulting from grain sprouting in the panicle or from immature grain from late developing tillers that are produced in the fall. Under favorable conditions following black layer formation, sorghum should be ready to harvest in 14 days or less at moisture levels below 18%. If harvest occurs before a killing frost the plant will have significant green leaf area that may make harvest difficult. In these cases growers may want to consider using gramoxone, defol, or other harvest aids to kill the plant and associated weeds prior to harvest. These harvest aids can help reduce grain moisture and ensure a timely harvest.
One of the reasons often cited for not harvesting in a timely manner is the cost of drying corn to the proper moisture levels for storage. If the crop is to be stored for any given period and if fungal growth is to be stopped or reduced, moisture content in sorghum should not exceed 13.5%. Because early harvest is done when grain moisture often exceeds 17%, drying is necessary. Grain drying costs can be estimated by the following equations:
Energy cost ($/dry bushel) = [(LP gas price X 0.02) + (Electricity price X 0.01)] X (initial moisture - 13.5)
Energy cost ($/wet bushel) = Energy cost per dry bushel X (100 - initial moisture)/86.5
These calculations are based on the fact that it takes 0.02 gal of LP gas and 0.01 KWH of electricity to remove 1% moisture per bushel.
Keep in mind these costs do not cover the cost of the drying equipment, extra labor involved in operating a dryer, or in grain shrinkage (weight loss caused by removing moisture and handling). Sorghum has a small seed with less pore space in the grain. Therefore, air does not move through the grain as easily as it does with a large seeded crop such as corn or soybean. When using bin, batch or peanut driers growers should keep the depth of the grain being dried to a maximum of 24". This will improve drying efficiency and help avoid spots in the grain mass that are not dried to the target moisture. Maximum drying temperatures for grain sorghum are from 10 to 20 ° F less than those used for drying corn. This means that the time required to dry a batch of sorghum will be longer compared to corn. Bin aeration systems will require higher flow capacities compared to those used in corn and soybean in order to move air through the bin in a reasonable time period. Sorghum grain should be monitored more frequently than other grains to control moisture migration and to ensure that hot spots don't occur.
There is one primary reason to store grain - to increase net return. If the net return cannot be increased by storing grain, storage is a waste of time and effort, and becomes a risk. The major drawback to grain storage can be summed up by the following. The returns from storage are measured in pennies, the losses from losing just one bin to insects or mold are measured in dollars. If grain is to be stored for a long period of time, if frequent monitoring of the grain is not possible, or if the labor and time required to move grain to the marketplace is not available when needed, then commercial storage may be a better alternative.
The following questions should be used to determine if on-farm storage is necessary:
Stored-grain management is a long-term approach to maintaining post-harvest grain quality, minimizing chemical control inputs, and preserving the integrity of the grain storage system. To implement an effective management program, operators must understand the ecology of the storage system.
Storage management must focus on the following factor:
An excellent preventive post-harvest grain management approach is the SLAM system (Sanitize/seal, Load, Aerate, Monitor). These stored grain management strategies should include the following steps.